Pneumatic actuating cylinders are used as actuators in various applications. In the field of commercial vehicle technology (trucks, buses), an advantageous application involves realizing an automatic clutch actuation in conjunction with automated gearshift systems via a pneumatic actuating cylinder. This eases the burden on the driver. The shift processes can be completely automated. Since compressed air is already available in commercial vehicles, the use of a pneumatic actuating cylinder is more favorable than a hydraulic actuating cylinder.
The important aspect of clutch actuation, particularly in the area of the clutch biting point, is to be able to perform sensitive actuating movements by means of the actuating cylinder. Traditional vehicle clutches have a force/travel curve, which initially rises roughly linearly up to a maximum value lying roughly around the clutch biting point. On the other side of the maximum value, the characteristic curve falls off again more or less sharply. This has the effect that the pressure built up in the actuating cylinder to achieve the maximum force is too high to hold a position close to the maximum value once the maximum value has been exceeded. This has hitherto been taken into account by relatively complex control algorithms in the actuating cylinder pressure control, such that a relatively sensitive position setting in the area of the clutch biting point is possible. Alternatively, pneumatic valves for pressure control in the actuating cylinder having different aperture cross-sections are connected to one another in parallel, in order thereby to optimise the sensitivity of the setting.